Finally got me a 'scope - Have some questions

[Supercap2F]

Hello Everyone!

Well as the title states, I finally got an oscilloscope. It's a 60MHz Leader 8060, which I got off of ebay for about $110. So first of all does anyone know where I can get it's user manual? I contacted Leader and they didn't have it, but they did give me the manual for some 'scopes like it. Or maybe if anyone has it they could send me a scan?

So, I found out that you have to adjust your probes to get the most accurate reading. The way this is done, is you hook up your probe to the 'scopes calibrating signal, and turn the variable capacitor on it tell you get a good sharp signal. Is all that right?

I have a BK precision PR-40 probe (actually it's my Dads). And it has a 15pF-40pF capacitance range. Does that mean that the input capacitance on the scope has to be somewhere between 15pF-40pF for the probe to get a accurate reading?

The Leader scopes before and after the 8060 have about a 20pF input capacitance. So I am assuming that the 8060 does too (or is really close to it). So if it does have a 20pF input capacitance then the probe should work good with it. Right? But if it does not, and I hook up the probe I have to it, will anything bad happen? Besides not getting a accurate reading.

Thanks Guys!! I may have some more question later.
Dan

 

[Harald Kapp]

So, I found out that you have to adjust your probes to get the most accurate reading. The way this is done, is you hook up your probe to the 'scopes calibrating signal, and turn the variable capacitor on it tell you get a good sharp signal. Is all that right?

Right. The probe's tip and the input of the scope both have a resistive and a capacitve component. This makes a frequency dependent voltage divider. By adjusting the capacitance in the tip you trim the impulse response.
As a funny coincidence I just posted this link to a collection of oscilloscope tutorials. This may interest you as well.

I have a BK precision PR-40 probe (actually it's my Dads). And it has a 15pF-40pF capacitance range. Does that mean that the input capacitance on the scope has to be somewhere between 15pF-40pF for the probe to get a accurate reading?

Not necessarily. This is, I assume a 10x probe? Then the resistance in the tip is 9MΩ, the scope has 1MΩ. The capacitances scale in the same ratio.

will anything bad happen

No, nothing bad happens apart from a distorted waveform. Just hook up the probe to the scope's test pin and try to adjust it. Most probably it wll turn out fine.

 

[Supercap2F]

Thanks Harald, those tutorials will be very helpful!

This is, I assume a 10x probe?

Yes, it has a switch on the side where you can select 1x 10x and REF.

No, nothing bad happens apart from a distorted waveform. Just hook up the probe to the scope's test pin and try to adjust it. Most probably it wll turn out fine.

Cool! I hoped nothing bad would happen.

EDIT: Is there anything wrong with buying one of those cheep probes off of ebay?

Regards
Dan

 

[KrisBlueNZ]

I tried Googling Leader 8060 oscilloscope user manual and found a link to a manual for the 8050 model which is similar: http://www.tequipment.net/pdf/Leader/LS8050_manual.pdf. If you try a bit harder than I did, you might find the right one.

EDIT: Is there anything wrong with buying one of those cheep probes off of ebay?

I wouldn't touch them with a ten foot pole personally. It's easy and cheap to make something that LOOKS like a scope probe but performs really badly. And when it's easy and cheap to make something that looks like the genuine article, and works, in a limited way, there are companies without reputations to protect that will do it.

Dave Jones of eevblog (see https://www.youtube.com/user/EEVblog) has some good information - on everything, really, but also specifically on scope probes. Learn more than you ever wanted to know here: https://www.youtube.com/results?search_query=eevblog+oscilloscope+probes

 

[Supercap2F]

Hey Kris!

I tried Googling Leader 8060 oscilloscope user manual and found a link to a manual for the 8050 model which is similar: http://www.tequipment.net/pdf/Leader/LS8050_manual.pdf. If you try a bit harder than I did, you might find the right one.

I spent hours looking for the 8060 manual, with no results.

I wouldn't touch them with a ten foot pole personally. It's easy and cheap to make something that LOOKS like a scope probe but performs really badly. And when it's easy and cheap to make something that looks like the genuine article, and works, in a limited way, there are companies without reputations to protect that will do it.

OK, I thought they might be junk. Do you know where I could get a good price on a probe, that's not total junk?

Thanks very much!
Dan

 

[KrisBlueNZ]

Probably just Google test equipment suppliers in your state or city. Any company that sells oscilloscopes will sell probes separately, and will sell good quality probes, because anyone who buys an oscilloscope and gets crappy probes would be very unhappy and would come straight back. Not like someone who has just spent $10 on a pair of probes from an anonymous supplier somewhere in Shenzhen and probably won't even bother posting bad feedback.

 

[(*steve*)]

I spent hours looking for the 8060 manual, with no results.

It is also worth checking the sticky post in the manuals and datasheets section. It has a list of a few places which have old manuals.

Having said that, I've checked a few and turned up nothing either.

 

[Supercap2F]

OK, so my 'scope got here today. Here's the front:



Besides needing a good cleaning, it's in really good cosmetic condition. I hooked it up to the calibration signal, and after adjusting my probe here's what it looked like:



When I adjusted the probe everything went OK. But then I moved the scope into a different room, then new room has carpet where as the old one had tile. So after a while I decided to try to get the wave form a little bit more sqaure. So I stuck the screw driver into the probes compensation variable capacitor, upon which the screen looked like this:



I pulled the screw driver out of the variable capacitor and the screen went back to normal. Then later I flipped the AC/GND/DC switch to AC position (it was at the DC position before), the waveform stopped moving across the display, and froze in it's current position. I then moved the scope back to the room with tile and flipped the AC/GND/DC switch to the AC position again, and the waveform kept moving along the display as normal. So do you think that the flooring may have been what made it act weird? Or do you think it was something else, like maybe the wiring in the room with the carpet, is screwed up? Also in the room with the carpet, I had the 'scopes power cord running through a extension cord. Do you think that could have made a difference?

Thanks so much!!
Dan

 

[Supercap2F]

OK, there was a kind of switch thingy on the back of the scope, it was set to the 100VAC position. I switched it to the 120VAC position (because the wall voltage here is a lot closer to 120VAC then 100VAC). And now when you flip the AC/GND/DC switch to the AC position the waveform keeps moving across the display. But when I stick the screw driver into the variable capacitor on the probe, it still makes the waveform look really noisy (although not as bad as before).

I'm starting to have doubts about this 'scope being in the "used, working order" the seller said it was in. It seems to not be working right. Like when I flip the 'V mode' switch to CH1 it displays all three traces. Shouldn't it just display one trace? Also when I flip it to CH2 it displays all three traces. But when I flip it to dual, it displays only two traces. What do you guys think? From the reading the 8050 manual, it seems as though when it's in the CH1/CH2 position it should only display one trace.

Thanks for your time!
Dan

 

[Supercap2F]

Well I asked a friend who used to work on tektronix 'scopes, about it. He said that the CRT was almost completely worn out, and the V mode switch is most likely worn out too. The weird noise that is on the trace when I try to calibrate the 'scope probe, is something wrong with the mains in that room. Also from what he said, the 'Delayed time mult' is screwed up. There's screen burn on the CRT too.

Thanks for your time Guys
Dan

 

[KrisBlueNZ]

Well I asked a friend who used to work on tektronix 'scopes, about it. He said that the CRT was almost completely worn out

"Worn out"? That's not a very technical term. What does he mean? Is he talking about the burn-in? Or does he mean that it's low-emission? Is it dim and out-of-focus? Did he check the filament voltage?

and the V mode switch is most likely worn out too.

Switches can be replaced you know...

The weird noise that is on the trace when I try to calibrate the 'scope probe, is something wrong with the mains in that room.

I was thinking it migh be a bad earth. Have you checked?

Also from what he said, the 'Delayed time mult' is screwed up.

Another highly specific, technical term.

If there's something genuinely wrong with the CRT, you might as well bin it (or auction it for parts). But I'd hate to see you throw it away when it could be repaired. Repairing your own oscilloscope is a great achievement to have under your belt.

 

[(*steve*)]

Did he look at it in person? Or did he look at pictures? (And work on, or work with?)

The screen burn is cosmetic, likely too is a "worn out screen". Can you adjust the intensity and focus to get a sharp trace? (Do these controls work as expected?)

The extension cord *may* have made a difference if it was incorrectly wired. But I'd also check that someone hasn't disconnected the ground connection too (or that your ground pins are correctly connected in that room).

The switch may be worn or dirty. First try moving it back and forth a few times. If that doesn't help, after the scope has been off for 24 hours, open it up (carefully) and spray some contact cleaner onto the switch. Also take a look inside to see if there's anything obvious wrong (stuff broken, burn marks, swollen caps, etc.) Oh and check the ground connection.

Keep your fingers away from anything that connects to the tube, ESPECIALLY the big insulated wire connected to the side of the tube.

 

[Supercap2F]

Hello Guys!

Did he look at it in person? Or did he look at pictures? (And work on, or work with?)

I talked to him in person, and showed him the pictures, and told him what was happing. But no, he did not see the 'scope in person.

"Worn out"? That's not a very technical term. What does he mean? Is he talking about the burn-in? Or does he mean that it's low-emission? Is it dim and out-of-focus? Did he check the filament voltage?

The screen burn is cosmetic, likely too is a "worn out screen". Can you adjust the intensity and focus to get a sharp trace? (Do these controls work as expected?)

You have to almost max out the intensity to get a nice sharp trace (that's what made him think it was bad). No he did not check the filament voltage.

Switches can be replaced you know...

Yes I know, but I thought that type of switch would be quite hard to find.

I was thinking it migh be a bad earth. Have you checked?

Kind of. I measured form ground to the hot wire and got 120VAC. I also measured form ground to neutral and got about 1.5VAC. In the room that the 'scope worked fine in, from ground to neutral is about 0.2VAC.

Another highly specific, technical term.

The 'worn out' and 'screwed up' is just me rephrasing what he said. The delayed time mult appears not to be working form what he said about how it should work (he never told me if he thought it was bad or not). In all modes, adjusting it does 100% nothing.

If there's something genuinely wrong with the CRT, you might as well bin it (or auction it for parts). But I'd hate to see you throw it away when it could be repaired. Repairing your own oscilloscope is a great achievement to have under your belt.

The switch may be worn or dirty. First try moving it back and forth a few times. If that doesn't help, after the scope has been off for 24 hours, open it up (carefully) and spray some contact cleaner onto the switch. Also take a look inside to see if there's anything obvious wrong (stuff broken, burn marks, swollen caps, etc.) Oh and check the ground connection.

I thought about trying to attempt a repair, but I might just mess it up even more. Also I have already started the return process on ebay, but the seller is giving me some trouble.

Thanks for the help!
Dan

 

[(*steve*)]

I thought about trying to attempt a repair, but I might just mess it up even more. Also I have already started the return process on ebay, but the seller is giving me some trouble.

Did you pay via paypal?

Make sure you open a dispute.

If he said it was working, the V Mode switch is a significant part, and it certainly appears that's not working. And the problems you're having with very simple triggering is probably even worse.

It's a shame, because looking at that scope, it seems it would have been a pretty nice instrument. :-(

 

[KrisBlueNZ]

You have to almost max out the intensity to get a nice sharp trace (that's what made him think it was bad).

This can be caused by failure of high-voltage resistors that set the voltages on the grids in the CRT, including the resistors connected to the brightness control potentiometer.

 

[Supercap2F]

Did you pay via paypal?

Make sure you open a dispute.

No I did not pay with paypal. But I did open a dispute.

This can be caused by failure of high-voltage resistors that set the voltages on the grids in the CRT, including the resistors connected to the brightness control potentiometer.

Good to know! But I think I will return it anyway.

Do you guys know anything about Kenwood 'scopes? They have one called the CS-5165 and it looks exactly like the Leader 8060.

Thanks for your time!
Dan

 

[Supercap2F]

Hey Guys!

Just thought I would post an update... I got ebay to make that guy refund my cash, so I bought another one. It's a BK precision 2260 cursor readout oscilloscope. It got here today and appears to be working perfect!! Here's the front:

And if your interested, here are some more photos:

I'll have my friend look at it sometime to confirm that it's working fine.
Dan

 

[(*steve*)]

That is a very nice scope. And BK Precision is a great manufacturer of test equipment.

Now I'm jealous.

Do you have a manual for it?

 

[KrisBlueNZ]

Very nice indeed. I want one!

 

[Supercap2F]

I had my friend look at it, and he said it was working great!

No I don't have the manual for it.. But I did find the manual for the 2125 which is a lot like it.

Best of all I got it for only US $130!
Dan